The present invention relates to a dual-injector fuel injection engine in which fuel is injected into a combustion chamber and intake passage from respective injectors.
Generally, in a conventional automobile engine, one fuel injector is provided to each cylinder. In an engine of this type, an injector which injects fuel directly into a combustion chamber and an injector which injects fuel into an intake passage may be provided in order to improve the output and fuel cost, as disclosed in, e.g., Japanese Patent Laid-open No. 11-315733 (to be merely referred to as reference 1 hereinafter) or 2002-48035 (to be merely referred to as reference 2 hereinafter).
In the engine described in reference 1, an in-cylinder injector which injects fuel into the combustion chamber is attached to that lower end of a cylinder head which is close to a cylinder block. An injector which injects fuel (light oil) into an intake passage is attached to that side of the cylinder head which is opposite to the in-cylinder injector across an intake port.
The engine described in reference 2 is a multi-cylinder engine. An in-cylinder injector is arranged at the lower end of a cylinder head. An intake pipe injector which injects fuel into an intake passage is arranged in an intake manifold attached to the cylinder head.
The intake manifold extends upward from a side portion of the cylinder head and then to the other side of the cylinder head across a portion above the cylinder head. In the intake manifold, a surge tank is arranged above the cylinder head, and a throttle valve is arranged in the vicinity of the upstream of the surge tank. A supercharger is connected to the upstream of the throttle valve through an intake pipe.
The two types of injectors shown in reference 2 are attached such that delivery pipes are fitted in their ends opposite to the fuel injection ports, and the fuel is supplied from the delivery pipes. Of the two types of injectors, the intake pipe injector is attached to the outer side of that curved portion of the intake manifold which is curved beside the cylinder head and extends vertically.
An engine as described in reference 1 or 2 in which each cylinder is provided with two injectors has a larger number of injectors than in a general engine. Accordingly, the number of assembling steps increases to make the assembly cumbersome. More specifically, when actually manufacturing an engine of this type, operation of attaching the intake pipe injector and its delivery pipe to the engine and operation of attaching the intake manifold to the cylinder head are performed almost simultaneously in a narrow area. Hence, until one of the two operations ends, the other operation must wait. The intake manifold must be attached and detached in maintenance of the intake pipe injector. The problem of overlapping operations thus occurs not only in the manufacture of the engine but also in the maintenance as well.
As shown in reference 2, often, the intake pipe injector and its delivery pipe are connected to each other by fitting the intake pipe injector in the delivery pipe, and they are sealed by a seal member such as an O-ring. If the intake pipe injector and its delivery pipe are aligned incompletely, fuel may leak from the sealed portion partly because the fuel is pressurized excessively.
Therefore, an engine in which each cylinder is provided with two injectors should be assembled easily and appropriately without requiring overlapping operations, as described above.
When an intake pipe injector is to be mounted in an engine of this type readily, the intake pipe injector should not extend outside the intake manifold to make the engine bulky, as in the engine shown in reference 2.